Millions of Americans will cross 'structurally deficient' bridges this weekend

The north end of the Interstate 5 bridge crossing the Skagit River lies collapsed in the water on Friday, in Mount Vernon, Wash. A truck carrying an oversize load struck the four-lane bridge on the major thoroughfare between Seattle and Canada, sending a section of the span and two vehicles into the Skagit River below Thursday evening. All three occupants suffered only minor injuries. At an overnight news conference, Washington State Patrol Chief John Batiste blamed the collapse on a tractor-trailer carrying a tall load that hit an upper part of the span.

The Washington state bridge collapse that spilled two cars into the Skagit River could give Americans pause as they hit the roads for Memorial Day holiday travel.

With good reason.

This weekend, millions will cross 66,000 bridges that the federal government has deemed "structurally deficient," meaning key elements are in poor condition.

The Federal Highway Administration hastens to note that label doesn't mean they are unsafe or in danger of collapse, but transportation advocates say it highlights a growing crisis of aging infrastructure, deferred maintenance and rebuilding, and design flaws.

"We don't expect an epidemic of collapses — that's the extreme," said Dan Goldberg, communications director for Transportation for America, a coalition that identified the busiest deficient bridges in the nation in a 2011 report.

"We are going to see probably some more of this, but the more likely scenario is contending with the issues of decay that happen before the collapse."

Big potholes, weight restrictions and lane closings are some of the inconveniences bridge users face unless reconstruction and replacement is ramped up across the nation, Goldberg said.

The Interstate 5 bridge in Mount Vernon, Wash., which apparently crumpled after being hit by an oversized truck, was not on the Federal Highway Administration's structurally-deficient list.

Famed spans aren't the problem. San Francisco's Golden Gate, for instance, is in pretty good shape. The Brooklyn Bridge is undergoing a massive rehabilitation project to correct its deficiencies.

But hundreds of less glamorous bridges — many of them generic overpasses that take commuters over cross streets or other highways — remain vulnerable.

Here are six crossings, together used by more than 1 million vehicles each day, that don't make the grade:

Maryland DOT

A view of I-695 crossing over Liberty Road in Maryland in August 2012.

I-76 over Klemm Ave. in Gloucester, N.J.: The deck and superstructure are in poor condition on this 11-lane interstate overpass that dates to 1956. More than 191,000 vehicles use it every day, and $30 million has been earmarked for deck replacement.

IS-695 over Milford Mill Road in Baltimore, Md.: Built in 1961 and reconstructed in 1979, this eight-lane overpass on the Baltimore Beltway has a deck and substructure in poor condition. But good news for nearly 190,000 vehicles that cross each day: It will be replaced in a two-year project starting this summer.

Halona St. Bridge in Honolulu, Hawaii: Built in 1938, this slab bridge over the Kapalama Canal is not slated for replacement until 2019. Some 184,000 vehicles travel the two-lane crossing, which has a deck and substructure in poor condition.

Colorado DOT

A view of the I-70 bridge over Havana Street in Denver, Colo. E-17-JP

I-70 over Havana St. in Denver, Colo.: This 10-lane structure, which has a deck and substructure in poor condition, is slated for a rebuild in the next few years. Built in 1964 and reconstructed in 1978, it services 183,000 vehicles a day.

I-278 approach to the Verrazano-Narrows Bridge in Staten Island, N.Y.: On an average day, 182,700 vehicles take this overpass to a majestic double-decker bridge. The substructure of the two-lane approach, built in 1961, is in poor condition.

I-95 over Hendricks Ave. in Jacksonville, Fla.: The deck is in poor condition on this nine-lane section of interstate that handles 121,000 vehicles a day. Built in 1959 and reconstructed in 1989, it is undergoing a replacement.

Source: Information about the structures was compiled by Nationalbridges.com, a website that analyzes data in the Federal Highway Administration's national bridge inventory.

A section of the Interstate 5 bridge over Washington's Skagit River collapses, sending cars into water below. NBC's Chris Daniels reports.